The epidemiology of P. aeruginosa in cancer patients and the influence of various factors such as host immune response and antibiotic resistance on the pathogenicity of this bacterium in cancer patients are the prime objective of this study. Nonagglutinating antibodies have been demonstrated in the sera of patients who had been colonized and/or infected with P. aeruginosa. Protective capabilities of these antibodies are under investigation. Kinetics of nonagglutinating antibody response in cancer patients, burn patients, and cystic fibrosis patients immunized with pseudomonas vaccine are in progress. An identification schema developed in our laboratory has been used to speciate approximately 1000 strains of the most frequently recovered Pseudomonas spp. other than P. aeruginosa. A schema for the identification of less common Pseudomonas spp. and Alcaligenes spp. is being evaluated.